fx, with a wallet.

$ curl -fsSL https://www.fx402.dev/setup.sh | bash

fx402
 x402_discover twit.sh
  GET /users/by/username · 0.005 USDC · x402  GET /users/search · 0.01 USDC · x402  33 more endpoints
 x402_fetch twit.sh/users/by/username?username=shafu0x  402 Payment Required
   Pay 0.005 USDC on eip155:8453 to 0x8f3a…c21b  for twit.sh/users/by/username? Wallet balance 4.982. 
  ❯ Pay     Sign and retry with PAYMENT-SIGNATURE    Cancel  Do not pay 
  paid · 200 OK · 0.005 USDC · 1.2s 

why

I love using fx. It is so fast. I wanted to see how fast it would be at calling x402 APIs as native tool calls, not as an MCP.

fx402 speaks x402, the open payment protocol built on HTTP 402. When the agent meets a paid endpoint it discovers the price, asks you, pays in USDC on Base, and keeps working. No keys, no accounts, no subscriptions.

how it works

Four tools. There is no MCP server to spawn and no handshake before the agent can pay.

  • x402_discover · list the paid endpoints on an origin, with prices
  • x402_check · read one endpoint's schema and exact price
  • x402_balance · read the wallet's USDC balance on Base
  • x402_fetch · pay for a request and return the response

your keys

  • The wallet is generated once at ~/.fx/wallet.json and never overwritten.
  • The private key never leaves your machine.
  • Every payment needs an explicit approval in the terminal. Without a TTY, fx402 refuses to spend.
  • Payments are USDC on Base, signed with EIP-3009.

credit

fx402 is a fork of vercel-labs/fx, built by the team at Vercel. All of the speed is theirs. Apache-2.0.